Light-weight gypsum products



I06. COMPOSITIONS,

COATING OR Patented Apr. 17, 1928.

UNITED STATES Eaatai PATENT OFFICE.

CARLISLE K. RODS AND MUBRELL G. ALLISON, OF FORT DODGE, IOWA, ASSIGNORS TO UNITED STATES GYPSUM COMPANY,

ILLINOIS.

OF CHICAGO, ILLINOIS, A CORPORATION 01' LIGHT-WEIGHT GYPSUM PRODUCTS.

No Drawing.

5 Gypsum has been used for some time in the manufacture of roof tile, floor tile, partition block, plaster board and wallboard and it is an object of this invention to increase the fire resisting or insulating qualities or structural strength and reduce the weight.

In accordance with this invention a small quantity, approximately less than five percent, of a soluble silicate. such as sodium 16 silicate. is a cg Q tie au in wa er W1 1 VVEICll calcined pgpsui n 'is mi xed io'r' producing gypsum ar 1c es w llCh will bring about a marked mcrease 1n the consistency of the mass, or, in other words, it will require 2 more water to bring the mass to the point of good working qualities. The quantity of water which the calcined gypsum will carry determines the weight per unit volume of the dried product. The function of the silicate is shown by the reaction Na SiO CaSO =Na SO CaSiO The product calcium silicate (CaSiO is a elatinnus, insolnblemcompmmdmhich 80 hol s a large percentage of its weight as water. The fact that this compound absorbs a portion of the water used in gauging the calcined gypsum explains the rise in a consistency of the mixture. The method of utilizing this reaction is very simple. A

solution of sodium silicate is simply added to the gauging water to which the calcined psum is added in sufiicient quantities to o tain good working qualities or normal consistency. The calcium silicate formed by the reaction is very intimately and homogeneously dispersed throughout the mass. The wet mass may be handled in the same Application filed October 23, 1924. Serial No. 745,419.

clued sum will raise the consistency from {6 cc. 110 to 85 cc., and at the same time the bulk of the mass js g onsiderably ingaase .ntesib al minquatg tiaous preci itate of calcium silicate. The above proportions "eur pmaee a wallboard weighing about 1700 pounds per 1000 sq. ft. The decrease in weight of the dried product is approximately proportional to the quantity of silicate used. The strength of the set material is somewhat reduced by additions of sodium silicate in excess of 5%. due to the large percentage of inert calcium silicate content, but the use of more than this quantity appears to be unnecessary.

hat we claim is:

1. A composition of matter composed of one hundred parts of hydrated calcium sulphate combined with about 2.3 parts of sodium silicate and water resulting in an expanded bulk of calcium sulphate containing sodium sulphate, calcium silicate and water.

2. The process for increasing the bulk and decreasing the weight of gypsum prod-' ucts which consists in adding 2.3 parts by weight of a solution of sodium silicate to the gauging water therefor, in mixing it with one hundred parts of calcined gypsum, in rendering plastic the gypsum and forming the product of the resultant mass, and in allowing it to set.

CARLISLE K. ROOS. MURRELL G. ALLISON. 

